Duncan , Oklahoma -LRB- CNN -RRB- -- Justin Boyles lay in bed , exhausted and depressed . His 385-pound body sank into the mattress with each breath he took . I have diabetes , he thought in disbelief .

His 6-year-old daughter , Autumn , crawled on top of the king-sized comforter and stared at him with bright blue eyes .

`` Daddy , will you get up and play ? ''

`` No , baby , I 'm tired . ''

She sat back to think . Her mom had tried to explain why Justin was so sad , but Autumn did n't really understand diabetes or its dangerous implications .

`` Daddy , are you ever going to be healthy enough to ride a bike with me ? ''

The question broke Justin 's heart . Tears started to roll down his face . `` Yes , very soon . I promise , '' he said .

`` Do you pinky promise ? '' she asked , holding out her tiny finger .

Justin looped his last digit around hers and made the decision to change his life .

All kinds of excuses

Shanon and Justin Boyles were high school sweethearts . The first time they hung out at 16 , Justin took Shanon to church . He was smart , polite and made her laugh -- three qualities that helped Shanon overlook his size .

`` As long as I can remember , I 've been overweight , '' Justin says . `` I remember as a child coming home after school and having a stack of cookies and a giant glass of milk every day . ''

In high school Justin weighed close to 250 pounds ; he was considered obese even at 6 feet 1 . As an adult he lived on fast food and spent most of his nights as a security guard sitting down . He 'd eat dinner at work -- frozen burritos , burgers and fries -- then stop off at Taco Bell on the way home for the advertised fourth meal .

`` I was really kind of in my own little hole , and I did n't want to get out or do anything , '' he says .

Shanon became worried . Any time their extended family tried to get together for a birthday party or holiday , Justin refused to go .

`` He would have all kinds of excuses , '' she says . `` He was really depressed . He was down on himself real bad . ''

Most concerning was his lack of time with Autumn , who got upset when her father would n't play outside .

`` She loves him . He 's her hero , '' Shanon says . `` I -LSB- knew -RSB- why he was feeling that way ... but there was nothing I could do about it . ''

Small steps for a big change

Since his diagnosis with type 2 diabetes in March -- and his pinky promise to Autumn -- Justin has lost more than 65 pounds . He walks around his neighborhood whenever he can and makes sure to do the little things like taking the stairs and returning his shopping cart . The family is also eating better with more vegetables , leaner meats and less sugar . For example , at dinner Justin usually eats a spinach leaf salad with tuna or baked chicken with broccoli . Shanon joins in ; she 's lost 20 pounds in less than six months on the new diet .

The family recently took a trip to the Oklahoma State Fair and walked around all day , something they never would have done last year .

`` I no longer lay in bed thinking that my weight is just too much to overcome , '' Justin says . `` I enjoy being out with family and friends and having a good time . ''

He only weighs in once a month to avoid becoming obsessed with the numbers on the scale . He hopes to get down to 200 pounds , a weight at which his doctor said he would probably be able to go off his medications .

`` I just want him to be healthy and happy . I do n't care what weight he 's at , '' Shanon says .

The couple raised more than $ 7,500 for the American Diabetes Association 's `` Step Out : Walk to Stop Diabetes '' in Oklahoma City on September 14 . Their team wore matching black T-shirts with a new slogan : `` Do you pinky promise ? ''

On his website Justin has included a section where he asks readers to make their own promises -- to themselves or to their family -- to get healthy .

'' -LSB- Autumn -RSB- taught me that you can do anything you put your mind to , '' he says . `` It does n't take a big giant step.It takes doing a little something . ''

Justin still has a long way to go in his weight loss journey . But rest assured that he 'll keep going -- you just do n't break a pinky promise , especially one made to your little girl .

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Justin Boyles learned he had type 2 diabetes in March 2011

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Since making a promise to his daughter , Boyles has lost more than 65 pounds

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Boyles raised $ 7,500 for the American Diabetes Association 's `` Step Out : Walk to Stop Diabetes ''